Turkish police fired teargas and water cannon to break up a protest outside a court in Ankara over the handling of a trial of a policeman accused of killing a demonstrator earlier this year.
A group of about 2,000 protesters wielding sticks descended on the court entrance after a ruling that the accused officer was not arrested, prompting police to intervene, a Reuters news agency witness said.
Several protesters were wounded and 18 detained, according to local media reports. Police in the Turkish capital declined to confirm the arrests and the crowd was later dispersed.
The officer in question, Ahmet Sahbaz, is accused of killing 26-year-old anti-government demonstrator Ethem Sarisuluk, in June during a wave of nationwide anti-government demonstrations set off by a tough police response to a protest over the redevelopment of Gezi Park in Istanbul.
'Excessive use of force'
Demonstrators armed with rocks and fireworks fought nightly against police firing tear gas, water cannon and pepper spray with the worst of the violence centered in Istanbul and Ankara.
Six people, including a police officer, had died during the weeks of unrest.
Turkish officials defended the police response but said such abuses will be investigated.
"You have the opposition, the protestors as well as international human rights group accusing the Turkish police of using sheer brutality and an excessive use of force," Al Jazeera's Omar Al Saleh reported from Istanbul.
"Now the government rejects that and says those were exaggerated claims but they did say that they will put some of the accused police officers on trial."
Amnesty International said this month that Turkish authorities had committed widespread rights abuses during that time, beating, harassing protesters, and the excessive use of tear gas.
The clashes have been one of the biggest challenges to Prime Minister Tayyip Erdogan's decade-old rule, who while maintaining relative popularity has also seen an increase of many who believe he has become an authoritarian dictator.